Manufacture of electric incandescent lamps having coiled-coil filaments



- 28, 1937. B. P. DUDDING ET AL 2,103,933 MANUFACTURE OF ELECTRIC INCANDESCENT LAMPS HAVINGCOILED 06in FILAMENTS f Filed April 14, 19:57

, "Inventors: Bernard F? Dudcling;

Then". Attorney.

Reginald L eds,

t. ML 4 '15 process; usually it contracts. This change of mm. in diameter and the pitch of the secondary 15 r 25 which the filament is supported at points interbetween the ends supported by the support wires 25 5 3o comparatively closely in the perpendicular dilying in planes perpendicular to the plane of 30 55 erence t t e o p ny drawing although, loops being elongated in the direction in which 55 Patented Dec. as, its? 2 103,93 v

Application April 14, 1937, Serial No. 136,940

' In Great Britain March 6, 1936 2 OJ L 7 (01. 176-39) This invention relates to the manufacture of apart from the elongated loops it follows a preelectric' incandescent lamps having coiled-coil vailing practice in the art. In the drawing, Fig. filaments. g 1 is a perspective view of a lamp embodying the I In the usual process of manufacturing these filament supporting means comprising our inlamps, the conversion of the plain wire'to the vention; Fig. 2 is a somewhat diagrammatic plan 5 filament, ready for mounting in the lamp, is conview of the filament and its supporting structure;

ducted wholly at temperatures much lower than and Fig. 3 is a perspective view showing a porthe filament attains in operation. The filament tion of the coiled-coil filament and one of'the is mounted in the lamp and then aged by passsupporting loops therefor. The lamp concerned ing current through it so as to heat itto a temis a 240 volt 40 watt lamp. perature higher than any to which it has been The diameter of the wire is 0.0232 mm.; it is subjected during its formation from plain wire. wound on a primary molybdenum mandrel 0.045 It is well-known that the filament is apt to mm. in diameter with a pitch of0.038 mm. or change its length during this final, or aging 164 per cent. The secondary mandrel is 0.210

mm r -ms i- P ATE NT OFFICE;

length is apt to be accompanied by the develophelix is 0.176 mm. or 192 per c n there are 153 ment of local irregularities of pitch, especially turns in this helix, successive filaments being if the filament is supported at points intermediate spaced along the mandrel. The filaments are between its ends by pigtails, which may hamper heated on the mandrel to 1500 C. for ten seconds free contraction. The object or this invention is and cut to length; the mandrels are dissolved out. 20

to provide a method of supporting the filament Each filament is now mounted in a lamp, as which decreases the chance of serious irregularishown in the accompanying drawing. I is the ties arising from the change of length. filament as originally mounted, with its ends sup- According to the invention the supports by ported by the leads 2,3 and the part intermediate mediate between its ends are loops, elongated in 4 which are 0.1 mm. in diameter and are spaced that direction in which the filament will tendto 40 apart from each other and the ends. The move relatively to the supports in virtue 01' its inner ends 5 of thewires are held in the glass contraction on aging, but fitting the filament stud 6; the outer ends are formed into loops 1 rection. the drawing.

Thus if the filament is to be mounted as a cir- According to the invention these loops. are not cular arc in a plane perpendicular to the axis of circular, as is usual, but are elongated in the rathe lamp, and if the lamp is to be burnt with its dial direction. They are 2.25 mm. long in the axis vertical, the supports are loops elongated radial direction and 1.25 mm. wide perpendicu- 35 in the direction of the radius of thecircle which, lar to the plane of the drawing.

passes through them, but fitting the filament When the filament is mounted and the lamp more closely in the direction parallel to the axis evacuated and filled with gas, the filamentis aged of the lamp. Thelength of the loops in the preferably with the plane of the drawing vertical 40 elongated direction is preferably chosen so that, and the stud above the filament. During aging 40 when the change of length is completed the filathe filament contracts 10.36 per cent in length, ment fits somewhat closely into the end of the so that the pitch of the secondary helix becomes loop which it approaches during the change. By- 0.158 mm, or 172 per cent. this means breakage of the filament owing to It has been found that elongated loops can be vibration is diminished. made on automatic machines such as are used 45 It is to be observed that, if the loops are made for making circular loops with only those modifiin this manner, they would oiTer no support to cations that are obvious to those skilled in the art. the filament, if the lamp were burnt with its axis What we claim as new and desire to secure by horizontal and with the filament below the axis. Letters Patent of the United States is: Accordingly this method of construction should 1. In an electric incandescent lamp havingan 50 not b adopted if it is ly that the lamp will arcuately mounted coiled-coil filament securely be burnt in this position. held at its ends, means for supporting said fila- One embodiment of the invention will now be ment intermediate its ends consistingof support des in detail, y y Of p with 'C wires having loops engaging said filament, said 10 support wires extending laterally outward from said lamp axis and having loops engaging said filament, said loops being elongated in the said lateral direction to provide for movement of the filament relatively to the supports by virtue of its contraction during aging but fitting the filament comparatively closely in the direction parallel to the lamp axis.

BERNARD PHINEAS DUDDING. REGINALD EDWARD LEEDS. 

